This invention relates to a transmission.
For industrial vehicles of the medium class up to about 30 t total weight and about 1000 Nm motor torque, manually shifted six-gear transmissions are preferably used. According to FIG. 1 such a six-gear transmission in countershaft design and progressive gear grading comprises one drive shaft 10, one output shaft 20 and one countershaft 30. An input constant gear pair K-1, K-2 is provided on the input side, which transmits the rotation of the drive shaft 10 to the countershaft 30. Upon the output shaft 20 are located the toothed gears 5-1, 4-1, 3-1, 2-1, 1-1 and R-1 as idler gears which are allocated respectively to the fifth gear, the fourth gear, the third gear, the second gear, the first gear and the reverse gear. The corresponding toothed gears 5-2, 4-2, 3-2, 2-2 and 1-2 are non-rotatably situated upon the countershaft 30. The toothed gear 1-2 is allocated both to the first gear and to the reverse gear R during an intermediate switch of an intermediate toothed gear R-3. The synchronizing clutch links S1/2, S3/4, S5/6 and SR are located upon the output shaft, the synchronizing clutch line S5/6 being moved to the right to engage the fifth gear in FIG. 1, the synchronizing clutch link S3/4 to the left to engage the fourth gear and to the right to engage the third gear, the synchronizing clutch link S1/2 to the left to engage the second gear and to the right to engage the first gear, the synchronizing clutch link SR to the right to engage the reverse gear and to engage the sixth gear the synchronizing clutch link S5/6 to the left to directly connect the drive shaft 10 with the output shaft 20.
About 95% of all transmission have the configuration of FIG. 1. Problems with these transmissions consist in the relatively great bearing span width and the shaft bendings associated therewith which, in turn, result in limiting the capacity for torque transmission. Transmissions of this kind required a large axial space and are thus relatively heavy and expensive. On account of the large masses to be synchronized, very strong shifting forces have to be applied.
Also six-gear transmissions are known where the constant gear pair is placed upon the output side. Problems with those transmissions consist in that, when the output shaft is not coaxially situated relative to the drive shaft, a comparatively high construction cost is required, but when the drive shaft and the output shaft are disposed coaxially to each other, a relatively large axial distance from the countershaft results.
The problem on which this invention is based consists in providing a transmission configured so that the manual shifting forces required are substantially reduced, the shafts are made short and the construction cost is small.
The essential advantage of the inventive transmission consists in that by virtue of the arrangement on the output side of two constant gear pairs (output constant group), the transmission is divided in two parts, namely, one part on the input side and one part on the output side whereby the constant gear pairs of the transmission part on the output side can be separately switched. Thereby two ratios are available in the transmission part on the output side. The switching between the constant gear pairs of the transmission part on the output side is automatic and externally controlled at a precisely defined point when preselecting the gear to be engaged. A sharp reduction of the manual shifting forces is advantageously obtained by the inventive idea, since almost all rotary masses are connected with the output and do not have to be synchronized together. The inventive transmission advantageously has a small number of gear stresses compared with the already known transmissions. All synchronizations that are switched in the driving operation under high differential rotational speed, especially that of the second gear, are located upon the input shaft. This arrangement is most favorable for the level of shifting force. One gear in the inventive transmission, preferably the highest gear, can be advantageously designed as direct gear. This increases the degree of efficiency. The inventive transmission is advantageously adequate for a high torque transmission, since its shafts are made short and therefore resist even high loads with only slight deformation. The instant transmission can advantageously be expended to a seven-gear transmission. By implementing a neutral position of the output group, the countershaft can act as a power take off on the output side by coupling any desired gear synchronization without added expense.